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Question

1)
A geological sample is found to have a Pb-206/U-238 mass ratio of 0.337/1.00. Assuming there was no Pb-206 present when the sample was formed, how old is it? The half-life of U-238 is 4.5 × 109 years.
A geological sample is found to have a Pb-206/U-238 mass ratio of 0.337/1.00. Assuming there was no Pb-206 present when the sample was formed, how old is it? The half-life of U-238 is 4.5 × 109 years.

2.1 × 109 years

1.4 × 1010 years

2.4 × 1010 years

7.1 × 109 years

7.3 × 1011 years
2)
A sample initially contains 8.0 moles of a radioactive isotope. How much of the sample remains after five half-lives?
3)The nuclide 6Li reacts with 2H to form two identical particles.
Identify the particles
4)
Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE?
Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE?

This reaction will be nonspontaneous at all temperatures.

This reaction will be nonspontaneous only at high temperatures.

This reaction will be spontaneous only at high temperatures.

This reaction will be spontaneous at all temperatures.

5)
Consider a reaction that has a positive ΔH and a negative ΔS. Which of the following statements is TRUE?
Consider a reaction that has a positive ΔH and a negative ΔS. Which of the following statements is TRUE?

This reaction will be nonspontaneous only at high temperatures.

This reaction will be spontaneous at all temperatures.

This reaction will be spontaneous only at high temperatures.

This reaction will be nonspontaneous at all temperatures.

6)
Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is TRUE?
Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is TRUE?

This reaction will be nonspontaneous only at high temperatures.

This reaction will be spontaneous only at high temperatures.

This reaction will be nonspontaneous at all temperatures.

This reaction will be spontaneous at all temperatures.

7)
For the following example, identify the following.
3O2(g) → 2O3(g)
For the following example, identify the following.
3O2(g) → 2O3(g)

a negative ΔH and a positive ΔS

a positive ΔH and a positive ΔS

a positive ΔH and a negative ΔS

a negative ΔH and a negative ΔS

8)
Which statement is true regarding the sublimation of dry ice (solid CO2)?
Which statement is true regarding the sublimation of dry ice (solid )?

ΔH is positive, ΔS is positive, and ΔG is positive at low temperature and negative at high temperature.

ΔH is negative,ΔS is positive, and ΔG is negative at all temperatures.

ΔH is negative, ΔS is negative, and ΔG is negative at low temperature and positive at high temperature.

ΔH is positive,ΔS is negative, and ΔG is positive at all temperatures.

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